This invention relates to an optical apparatus such as a camera which can detect its posture.
It is a common practice that a photographer changes the posture of camera from the horizontal or landscape posture (i.e., the transverse direction of the camera is parallel to the ground) to the vertical or portait posture (i.e., the transverse direction of the camera is normal to the ground) and vice versa in accordance with a position of an object or his/her preferred composition. To ensure precise shake correction control and focusing control, it has been appreciated to change sensing regions and other parameters for these controls in accordance with the posture of camera. Accordingly, it has been demanded to detect the posture of camera promptly and precisely.
U.S. Pat. No. 5,335,032 discloses a method for detecting the posture of a camera with respect to the gravitational direction based on a position of a shake correction lens adapted for shifting the optical axis of the taking lens. Specifically, the shake correction lens is freely movable when the shake correction lens is not driven (i.e., set at a free state). A position sensing device (PSD) or the like is provided in the camera to detect an extreme position into which the shake correction lens has freely moved and from which it is difficult to freely move further.
For this posture detection method, the PSD detects the extreme position where the shake correction lens is difficult to freely move further, thereby judging the posture of the camera. Accordingly, it is impossible or hard to detect the posture of camera in the case that the shake correction lens has moved and stopped at a position slightly before the extreme position. Also, the posture detection is not feasible in the case that the camera is shaken. Further, there is the problem that the posture detection cannot be performed until the shake correction lens moves into the extreme position by the weight thereof.
Conventionally, a shake amount is detected by obtaining data about image within a predetermined single sensing region of the field of view, and comparing obtained image data with base an image data. However, satisfactory shake correction has not been accomplished in the arrangement where a single sensing region is fixedly set in the field of view. For instance, in the flash-assisted photography, it is preferable to detect a shake amount through an end portion of the field of view rather than through a center portion of the field of view. The shake correction on the fixed single sensing region cannot cope with versatile demands of shake correction which vary according to various photography conditions.
U.S. Pat. No. 4,904,854 and U.S. Pat. No. 5,264,889 disclose a method of selecting sensing regions necessary for auto-focusing in accordance with a camera posture. Specifically, according to the method of U.S. Pat. No. 4,904,854, when the camera is judged to be in a vertical posture, a lower sensing region of a plurality of sensing regions is suspended from use for auto-focusing control on the assumption that the lower sensing region is liable to sense an object closer to the camera than a main object. Also, according to the method of U.S. Pat. No. 5,264,889, when the camera is judged to be in a vertical posture, a sensing region which has no symmetrical corresponding sensing region in the vertical posture is suspended from use for auto-focusing control. However, these sensing region selections are carried out to prevent wrong auto-focusing, but not to reduce the calculation time for auto-focusing.